Many paper documents are promptly discarded after being read. Although paper is inexpensive, the quantity of discarded paper documents is enormous and the disposal of these discarded paper documents raises significant cost and environmental issues. Accordingly, it is desirable to provide, in embodiments, a new medium for containing a desired image and a new image forming method.
To address this issue, it is known to produce reimagable displays based on technologies such as encapsulated electrophoretic particles, multichromal beads, and/or liquid crystals. Examples of such electronic devices, known as electronic paper, are described in U.S. Pat. No. 5,723,204 to Stefik and U.S. Pat. No. 5,604,027 to Sheridon, each of which is incorporated herein by reference in its entirety.
Electronic paper technology uses electric energy to display desired images on display devices. Electronic paper technology is essentially based on electrophoresis, thermal rewritability, liquid crystal conversion and/or electrochromism, and is broadly divided into two categories. The first category uses a display device in which a liquid display element or a liquid containing a solid display element with particles dispersed therein is sealed between a pair of substrates. The other category uses a display device in which electroconductive particles of different colors serving as a display element and insulating particles are sealed between a pair of substrates each having an electrode and a dielectric layer laminated on a support.
Reimagable medias have been previously developed. Typically, such devices include stacked layers capable of showing different colors with cholesteric liquid crystals or Organic Light Emitting Diode (OLED) displays. Each of these technologies are expensive because each layer is filled with the active material under clean-room conditions, the pixels for each layer must overlap in order to properly display information (which requires complicated photolithographic techniques), and each layer requires its own set of electronic drivers.
Photochromism in general is a reversible change of a single chemical species between two states having distinguishably different absorption spectra, wherein the change is induced in at least one direction by the action of electromagnetic radiation. The inducing radiation, as well as the changes in the absorption spectra, is usually in the ultraviolet, visible, or infrared regions. In some instances, the change in one direction is thermally induced. The single chemical species can be a molecule or an ion, and the reversible change in states may be a conversion between two molecules or ions, or the dissociation of a single molecule or ion into two or more species, with the reverse change being a recombination of the two or more species thus formed into the original molecule or ion. Photochromic phenomena are observed in both organic compounds, such as anils, disulfoxides, hydrazones, osazones, semicarbazones, stilbene derivatives, o-nitrobenzyl derivatives, spiro compounds, and the like, and in inorganic compounds, such as metal oxides, alkaline earth metal sulfides, titanates, mercury compounds, copper compounds, minerals, transition metal compounds such as carbonyls, and the like. Photochromic materials are known in applications such as photochromic glasses, which are useful as, for instance, ophthalmic lenses.
U.S. Pat. No. 3,961,948 to Saeva, incorporated herein by reference in its entirety, describes an imaging method wherein visible light produces an image on a photochromic compound.
U.S. Pat. Nos. 6,358,655 and 6,365,312, each to Foucher et al. and incorporated herein by reference in its entirety, describe a marking material for generating images wherein the marking particle includes a photochromic spiropyran material.
Display devices comprised of a liquid crystal composition that is switchable between states, such as black and white, are known and described in, for example, U.S. Pat. No. 6,849,480 to Iftime et al.; U.S. Pat. No. 6,824,708 to Iftime et al.; and U.S. Pat. No. 6,767,240 to Iftime et al., each of which is incorporated herein by reference in its entirety.
It is desirable to provide a reimagable media that is cost-effective and relatively easy to produce.
It is desirable to provide flexible reimagable media that are capable of producing a multi-color display.
The disclosed embodiments are directed to solving one or more of the above-listed problems.